TryIntoJs trait and derive macro for it

[Nikita-str]

This Pull Request closes #3874

Notes

• I don't sure about conversion of HashMap into JsObject.
  Should it be converted into JsMap or into ordinary object { k1: v1, ..., kN: vN }?
  Or maybe I need to add a macro attribute to allow choose a way of conversion of Map types?

[HalidOdat]

Why do we need to have a separate derive and implementation for it we can have an automatic impl for it, that uses TryFromJs. Like the standard library does it: https://doc.rust-lang.org/beta/src/core/convert/mod.rs.html#788-815. Implementing TryFromJs should automaticaly implement TryIntoJs.

Am I missing something?

[Nikita-str]

@HalidOdat

TryFromJs converts JsValue into Rust types, so there will no such type that converts a Rust type via TryFromJs into JsValue.

In std mod we can have an object of any type as value in try_from.
In the definition of the trait we specifically have value: &JsValue.

So

• TryFromJs can make only JsValue --> Rust (value always JsValue)
• TryIntoJs can make only Rust--> JsValue (result always JsValue)

There is try_js_into fn that do the same as TryFromJs: converts JsValue into Rust type. (self is JsValue)

[HalidOdat]

Ahh, I see, yes that makes sense!

The PR looks good to me! :)

[codecov]

Codecov Report

Attention: Patch coverage is 33.91304% with 76 lines in your changes missing coverage. Please review.

Project coverage is 52.80%. Comparing base (6ddc2b4) to head (4be1d56).
Report is 276 commits behind head on main.

Files with missing lines	Patch %	Lines
core/macros/src/lib.rs	0.00%	52 Missing ⚠️
core/engine/src/value/conversions/try_into_js.rs	61.90%	24 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3999      +/-   ##
==========================================
+ Coverage   47.24%   52.80%   +5.55%     
==========================================
  Files         476      481       +5     
  Lines       46892    46791     -101     
==========================================
+ Hits        22154    24706    +2552     
+ Misses      24738    22085    -2653     

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[HalidOdat]

I don't sure about conversion of HashMap into JsObject. Should it be converted into JsMap or into ordinary object { k1: v1, ..., kN: vN }? [..]

I should probably be a JsMap by default, it's also more space efficient, since the properties are stored in an hashmap https://github.com/boa-dev/boa/blob/main/core/engine/src/builtins/map/ordered_map.rs#L36-L42, rather that in the shape and object storage.

[jedel1043]

Pretty impressive work! Looks really nice :)